Well I wasn't in my High School swim team as there were people better than me around, but I am more of a long-haul swimmer myself. I have done quite a few 5K swims (why can't they do it in MILES damnit! It's 3.15 miles) in the recent past for the school... and it's surprizingly easy - at least if you're used to it - once you get about a quarter of the way thru. I do everything long-haul in backstroke as it's my stroke of choice. My average time for the 5K is around 1:45. Notamazing, but not bad, and the stamina is more important, I believe, than the speed. Just don't stop!!! Keep going and as you go it really does get easier.
Say you have a 100ft pool - and therefore 150 lengths is 5K - the first 20 lengths are easy - the next ten are the worst of the whole thing - and then from then on in it gets easier provided you stick with the same stroke and get the rhythm going and keep it going. By length 100, you are on autopilot - but at least with me, nothing hurts by that point! And then, just to add insult to injury, when you get home do some situps - they keep you from being completely immobile the next day!!!
The flag at the end of the pool at 18 feet from the ends of the pool I believe - and the reason they are there is that, when you start to swim, (not everytime, just the first couple of times) you should count (when swimming backstroke) how many strokes it takes you to reach the end of the pool... so the idea is that you know exactly when to roll over and tumble turn to face, and then swim, the other way by instinct without hitting the end or having to do a stroke on your front - which is a disqualification 'offense'.
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